This invention relates to a furnace for the continuous heat treatment of refractory wire materials like a tungsten wire.
Appended FIG. 1 shows a typical example of conventional furnace for the continuous heat treatment of long wire materials. As shown in the drawing, a plurality of burners 2 are mounted in the wall of a furnace body 3 apart from each other in the running direction of a wire material 1. A fuel-air mixture introduced through a pipe 4 is supplied to these burners 2. Naturally, the wire material 1 is directly heated by the flame spurting from the burners 2. Further, a plurality of discharge ports 5 are provided apart from each other in the running direction of the wire material.
The conventional furnace of this type is defective in that the combustion gas spurting from the burner 2 tends to flow directly into the discharge port 5, resulting in failure to utilize effectively the free space within the furnace. Namely, the conventional furnace brings about a failure to utilize effectively the heat of the flame, leading to an increased fuel gas consumption. Further, the wire material running within the furnace is brought into direct contact with the flame spurting from the burner. This causes local over-heating of the wire material at the portions which have been brought into direct contact with the flame, leading to quality deterioration of the heated wire material and to an increased loss of the wire material caused by oxidation. Still further, the provision of a plurality of discharge ports renders it troublesome and complicated to mount heat exchangers for enhancing the thermal efficiency of the furnace, to mount cooling devices of the burners, etc., leading to a high manufacturing cost of the furnace.